Synopsis
Recognise evolving respiratory muscle pump failure early, measure ventilation rather than relying on oxygen saturation, and coordinate non-invasive ventilation, cough support and person-centred escalation.
- Neuromuscular weakness and severe chest-wall restriction cause ventilatory pump failure; breathlessness may be modest because patients cannot generate enough activity to expose limited reserve.
- Orthopnoea, unrefreshing sleep, morning headache, daytime somnolence, weak cough and recurrent lower respiratory infection can precede obvious daytime hypoxaemia.
- A normal spot oxygen saturation does not exclude nocturnal hypoventilation, falling vital capacity or impaired cough, so serial physiology and symptoms matter.
Key red flags
New drowsiness, respiratory acidosis, weak or absent cough, rapidly declining respiratory measurements or inability to manage secretions requires urgent senior respiratory and critical-care assessment.
Investigation priorities
Track global respiratory restriction and its direction over time.
Management branches
Progressive neuromuscular disease, severe chest-wall restriction or new symptoms of sleep-related hypoventilation.
- Establish baseline symptoms, sitting and supine respiratory measurements, cough effectiveness, bulbar function, daytime gas exchange and current respiratory infections.
- Arrange overnight oxygen and carbon-dioxide monitoring when symptoms, trajectory or respiratory-strength results suggest nocturnal hypoventilation despite acceptable daytime saturation.
Key medicines
Non-invasive ventilationIndividualised specialist settings used during sleep and extended as respiratory dependence evolves.
Mechanical insufflation-exsufflationPressures, timing and cycles are individually titrated and taught by the respiratory team.